Tetracyano-1,4-hydroquinone and tetracyano-1,4-benzoquinone

ABSTRACT

Processes for the preparation of tetracyano-1,4-hydroquinone and its conversion to tetracyano-1,4-benzoquinone via a disilver salt are disclosed.

This is a divisional of U.S. Ser. No. 07/472,920 filed Jan. 31, 1990,now U.S. Pat. No. 5,068,367.

FIELD OF THE INVENTION

This invention relates to improved processes for the preparation oftetracyano-1,4-benzoquinone and it's precursortetracyano-1,4-hydroquinone.

BACKGROUND

U.S. Pat. No. 3,114,756 issued Dec. 17, 1963, discloses the compositionof tetracyano-1,4-hydroquinone, a process for its preparation, thecomposition of tetracyano-1,4-benzoquinone and a process for itspreparation from tetracyano, 1,4-hydroquinone. The process leading totetracyano-1,4-hydroquinone originates from2,5-dicyano-3,6-dihalogeno-1,4-benzoquinones. It is stated that it isnot possible to introduce further cyano groups into2,3-dicyano-5,6-dihalogeno-1,4-benzoquinones or2,3-dicyano-5,6-dihalogeno-1,4-hydroquinones. Since2,3-dicyano-5,6-dichloro-1,4-hydroquinone is the product of the reactionof chloranil (tetrachloro-1,4-benzoquinone) with potassium cyanide, itis implied that chloranil would not be a suitable starting material fortetracyano-1,4-hydroquinone. The process for the conversion oftetracyano-1,4-hydroquinone to tetracyano-1,4-benzoquinone utilizes asreagent "nitrous gases." These same chemical conversions are discussedat length by K. Wallenfels et al., Tetrahedron, 21, 2239-2256 (1965) andAngew. Chem. 73, 142 (1961).

E. A. Braude et al., Journal of the Chemical Society (London) 1954, p3572 disclose that attempts to replace the chlorine atoms in chloranilwith cyanide groups from cuprous cyanide were unsuccessful.

L. Bucsis et al., Chemische Berichte, 109, 2462-2468 (1976) disclose theisolation of tetracyano-1,4-hydroquinone in 5% yield as a by-product inthe preparation of 2,3-dichloro-5,6-dicyano-1,4-hydroquinone from thereaction of chloranil with potassium cyanide. It is stated that, despitethe low yields, this route to tetracyano-1,4-hydroquinone is preferredover the route of Wallenfels et al. due to shorter cycle time andavailability of starting materials. There is neither disclosure norsuggestion of how to convert this low-yield process to a high-yieldreproducible process.

O. W. Webster et al., J. Org. Chem, 30, 3250 (1965), disclose thepreparation of tetracyano-1,4-hydroquinone fromtetracyano-p-phenylendiamine via the bis(diazonium) compound in 35%yield. The tetracyano-p-phenylenediamine starting material was itselfprepared in 3.7% yield from tetracyanoethane.

Thus, there exists no easily operable, reasonable yield route totetracyano-1,4-hydroquinone. Nor is there a known process for theconversion of tetracyano-1,4-hydroquinone to tetracyano-1,4-benzoquinonethat involves the use of stable, readily available reagents.

It is therefore an object of the present invention to provide a processfor the preparation of tetracyano-1,4-hydroquinone.

It is a further object of the present invention to provide processes forthe preparation of tetracyano-1,4-benzoquinone.

It is a further object of the present invention to provide novelelectron-transfer complexes of tetracyano-1,4-benzoquinone.

SUMMARY OF THE INVENTION

This invention provides a novel process for the preparation oftetracyano-1,4-hydroquinone comprising reacting atetrasubstituted-1,4-benzoquinone with a source of cyanide ion in asolvent comprising a lower alcohol selected for its ability to dissolveboth the source of cyanide ion and the tetrasubstituted-1,4-benzoquinonestarting material in a manner such that the cyanide ion is, at allstages of the reaction, present in stoichiometric excess.

This invention also provides a novel process for the conversion oftetracyano-1,4-hydroquinone to tetracyano-1,4-benzoquinone thatcomprises a) reacting tetracyano-1,4-hydroquinone with a silver salt toyield the disilver salt of tetracyano-1,4-hydroquinone, and b) reactingsaid disilver salt with an oxidizing agent to yieldtetracyano-1,4-benzoquinone.

This invention also provides a novel process for the conversion oftetracyano-1,4-hydroquinone to tetracyano-1,4-benzoquinone thatcomprises a) reacting tetracyano-1,4-hydroquinone with a tetraalkyl ortetraaryl ammonium salt to yield the corresponding ammonium salt oftetracyano-1,4-hydroquinone; b) reacting said ammonium salt with asilver salt to yield the disilver salt of tetracyano-1,4-hydroquinoneand c) reacting said disilver salt with an oxidizing agent to yieldtetracyano-1,4-benzoquinone.

This invention also provides novel, easily characterizable 1:1electron-transfer complexes of tetracyano-1,4-benzoquinone with electrondonors, for example, with ferrocene, substituted ferrocenes,tetrachalcogenfulvalenes and substituted tetrachalcogenfulvalenes andalso 1:1 charge-transfer complexes of tetracyano-1,4-benzoquinone withcompounds such as triphenylene, hexaaminobenzene and hexamethoxybenzene.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides improved yield process routes to the targetcompounds utilizing starting materials more readily available than thoseutilized in previously known routes. The reference by L. Bucsis et al.cites yields of tetracyano-1,4-hydroquinone from various substitutedquinones in the following quantities: from2,5-dibromo-3,6-dimethoxy-1,4-benzoquinone--3%; from2,3-dichloro-5,6-dicyano-1,4-benzoquinone--3%; from chloranil--5%; frombromanil--7%. The yield of tetracyano-1,4-hydroquinone from varioussubstituted quinones employing the process of this invention areapproximately doubled versus the yields reported in the prior art, forexample; from bromanil 18%; from2,3-dichloro-5,6-dicyano-1,4-benzoquinone--6%.

The prior art route to tetracyano-1,4-benzoquinone fromtetracyano-1,4-hydroquinone utilizes the rather obscure reagent "nitrousgases". The process of the present invention utilizes syntheticprocedures easily explainable to and readily reproducible by one skilledin the art.

The processes of the present invention are summarized in reactionScheme 1. ##STR1##

In Scheme 1, R signifies lower alkyl, containing up to about 8 carbonatoms; R¹ signifies cyano and R² signifies chloro, or R¹ equals R² andboth are equal to bromo, chloro, or cyano. R³ signifies a lower alkylgroup containing up to about 4 carbon atoms.

For the first process of the present invention, the conversion of atetrasubstituted-1,4-benzoquinone (1) to tetracyano-1,4-hydroquinone,(2) reaction conditions are important. Suitabletetrasubstituted-1,4-benzoquinones include bromanil, chloranil,2,3,5,6-tetramethoxy-1,4-benzoquinone, and2,3-dichloro-5,6-dicyano-1,4-benzoquinone. To secure the advantages ofthe present invention, it is preferred that the cyanide ion is always,and in all parts of the reaction media, in stoichiometric excess. Thisis most readily achieved by adding the tetrasubstituted-1,4-benzoquinonestarting material to a solution of the cyanide ion source. Preferably,this addition is carried out relatively slowly; for example, in apreparation involving 25 grams of bromanil, the addition was carried outover about one hour.

The solvent for the reaction is preferably a lower alcohol of up to fourcarbon atoms, and most preferably methanol. The prime criterion for thesolvent is that it provide at least some solubility for the source ofcyanide ion and for the tetrasubstituted-1,4-benzoquinone startingmaterial. It is preferable that the solvent be essentially free ofwater.

Temperature conditions for the reaction are not critical. The reactionis preferably carried out from about room temperature up to the boilingpoint of the solvent. Pressure limits for the reaction have not beenexplored. It is most convenient to carry out the reaction at ambientatmospheric pressure.

The source of cyanide ion can be any of a number of soluble cyanidesalts, for example, alkali metal (lithium, sodium or potassium) cyanideor ammonium cyanides, for example, tetraalkyl or tetraaryl ammoniumcyanides. The alkyl group present in the tetraalkyl ammonium cyanide cancontain up to about 8 carbon atoms.

It is important that the cyanide ion is always in stoichiometric excessduring the course of the reaction. That is, there must, in the case of,for example, bromanil, be at least greater than four moles of cyanideion per mole of bromanil present during the course of the reaction.Preferably a greater excess is employed. Preferably, a two-fold excessis employed, that is, for each mole of bromanil, eight moles of cyanidewould be employed.

Because of the tendency of the reaction that formstetracyano-1,4-hydroquinone to yield by-products or, in most cases, notto proceed to completion, the mode of isolation of thetetracyano-1,4-hydroquinone product is critical with regard to obtainingthat product in a pure, readily characterizable form. Isolation andpurification takes advantage of the propensity oftetracyano-1,4-hydroquinone toward salt formation and complex formation.For example, as described in example 1, the isolation and purificationof tetracyano-1,4-hydroquinone proceeds via a morpholinium salt, apyrene complex and a dioxane complex. The dioxane complex is thendissolved in water; the aqueous solution filtered to remove insolubles;the filtrate acidified to precipitate pure tetracyano-1,4-hydroquinonewhich may then be filtered or extracted with ether and recovered afterevaporation of the ether.

The process of the present invention of convertingtetracyano-1,4-hydroquinone (2) to its disilver salt (4) is carried outeither directly, with no intervening isolation step or indirectly, viaan isolated ammonium salt of tetracyano-1,4-hydroquinone (3).

In the direct route, a stoichiometric excess of a soluble silver salt isallowed to react with tetracyano-1,4-hydroquinone in the presence of asolvent. The silver salt may be, for example, silver triflate or silvernitrate. Silver nitrate is preferred.

Solvents suitable for use in this reaction include those capable ofdissolving both the selected silver salt and thetetracyano-1,4-hydroquinone. Preferred solvents are methanol,acetonitrile, or water, with water being most preferred.

The temperature of the reaction is not critical, although when usingcertain solvents, heating may be desirable to speed the dissolution ofreagents. The temperature range is from about room temperature to aboutthe boiling point of the solvent. The reaction is typically carried outat atmospheric pressure under an air atmosphere, although the use of aninert gas atmosphere is not precluded.

A stoichiometric excess of the soluble silver salt is required.Typically an amount at least about twice that required by the reactionstoichiometry is used.

In the indirect conversion of tetracyano-1,4-hydroquinone (2) to itsdisilver salt (4), the tetracyano-1,4-hydroquinone is first converted toa monotetra-substituted ammonium salt (3), isolated as such, and is thenconverted further to the disilver salt.

This conversion, which involves the reaction oftetracyano-1,4-hydroquinone with a tetra-lower alkyl ammonium salt,where lower alkyl signifies an alkyl group that may contain up to about8 carbon atoms, or a tetra-aryl ammonium salt, is carried out in asolvent capable of dissolving both reactants, for example water, a loweralkyl alcohol or acetonitrile. The preferred solvent is water.

The tetra-lower alkyl ammonium salt or a tetra-aryl ammonium salt, canpossess essentially any counter anion. Halides, especially bromide oriodide, are preferred as the counter anion.

The temperature range employed is from approximately room temperature tothe boiling point of the chosen solvent. The reaction is carried out atambient pressure and can be carried out under an air atmosphere,although the use of an inert gas atmosphere is not precluded.

The tetra-lower alkyl ammonium salt or a tetra-aryl ammonium salt isemployed in at least a stoichiometric amount, that is one mole oftetra-lower alkyl ammonium salt or tetraaryl ammonium salt, per mole oftetracyano-1,4-hydroquinone to yield the monoammonium salt.

The second step of this indirect conversion oftetracyano-1,4-hydroquinone to its disilver salt involves the conversionof the isolated tetra-lower alkyl ammonium salt or tetra-aryl ammoniumsalt. This reaction is similar to that described above for the directconversion.

A stoichiometric excess of a soluble silver salt is allowed to reactwith the tetra lower-alkyl ammonium salt or tetra-aryl ammonium salt oftetracyano-1,4-hydroquinone in the presence of a solvent. The silversalt may be, for example, silver triflate or silver nitrate. Silvernitrate is preferred.

Solvents suitable for use in this reaction include those capable ofdissolving both the selected silver salt and the tetra lower-alkylammonium salt or tetra-aryl ammonium salt oftetracyano-1,4-hydroquinone. Preferred solvents are methanol,acetonitrile, or water with water being most preferred.

The temperature of the reaction is not critical, although when usingcertain solvents, heating may be desirable to speed the dissolution ofreagents. The temperature range is from about room temperature to aboutthe boiling point of the solvent. The reaction is typically carried outat atmospheric pressure under an air atmosphere, although the use of aninert gas atmosphere is not precluded.

A stoichiometric excess of the soluble silver salt is required.Typically an amount at least about twice that required by the reactionstoichiometry is used.

The final reaction step in the route from tetracyano-1,4-hydroquinone(2) to tetracyano-1,4-benzoquinone (5) is the conversion of the disilversalt of tetracyano-1,4-hydroquinone (4), whether prepared by the director indirect route, to the tetracyano-1,4-benzoquinone (5) product.

This conversion is carried out by the oxidative action of an oxidizingagent on the disilver salt of tetracyano-1,4-hydroquinone in thepresence of a solvent.

Solvents suitable for use in this reaction are organic solvents that arenon-reactive to the oxidizing agent under the conditions of theoxidation reaction. This group of solvents includes, for example,ethylene dichloride, methylene chloride, carbon tetrachloride, hexaneand other aliphatic hydrocarbons. In general, acceptable solvents haveno site of unsaturation or other functionality capable of reacting withthe oxidizing agent under the chosen reaction conditions. A preferredsolvent is ethylene dichloride. The solvent is, preferably, free ofwater and oxygen.

Oxidizing agents suitable for use herein are halogens, for examplechlorine, bromine, iodine, iodine monochloride, iodine monobromide, andbromine monochloride. Bromine is the preferred oxidizing agent. Adriving force for the oxidation reaction is the formation andprecipitation of silver halide.

The reaction temperature range is from about room temperature to theboiling point of the solvent. The reaction is carried out underatmospheric pressure. It is desirable to carry out the reaction under anatmosphere of an inert gas, for example, argon or nitrogen.

A further aspect of the present invention comprises 1:1electron-transfer complexes of tetracyano-1,4-benzoquinone with electrondonors, such as ferrocene, substituted ferrocenes,tetrachalcogenfulvalenes and substituted tetrachalcogenfulvalenes, andalso 1:1 charge transfer complexes of tetracyano-1,4-benzoquinone with asubstituted aromatic compound, such as triphenylene, hexaaminobenzeneand hexamethoxybenzene.

The formation of charge transfer complexes and electron transfercomplexes from tetracyano-1,4-benzoquinone and appropriate complexingcompounds is carried out in an organic solvent selected for its abilityto dissolve both the tetracyano-1,4-benzoquinone and the complexingcompound, for example acetonitrile and tetrahydrofuran. Thecomplex-forming reaction is carried out at ambient pressures in atemperature range from approximately room temperature to the boilingpoint of the solvent. The complex-forming reaction is carried out underan inert atmosphere, for example, under nitrogen or argon.

The utility of tetracyano-1,4-hydroquinone is as an intermediate totetracyano-1,4-benzoquinone. The utility of tetracyano-1,4-benzoquinoneis as a very strong oxidizing agent, a hydrogen abstraction reagent, andas a reagent in the formation of charge and electron transfer complexes.The strength of tetracyano-1,4-benzoquinone as a hydrogen abstraction(dehydrogenation) agent exceeds that of2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), the use of which isdescribed by D. Walker et al., Chem. Rev. 1967, 67, 153 and H. D. Dieteret al., J. Org. Chem., 1980, 45, 1596. The charge electron transfercomplexes are extremely stable and are therefore useful in thepreparation of organic semiconductors.

The following examples illustrate the present invention, but are notintended to limit it in any manner. In the examples that follow,infrared spectra were recorded on a Nicolet 7199 Fourier transformspectrometer. Elemental analyses were performed by Oneida ResearchServices, Inc. (Whitesboro, NY).

X-ray crystal structure analysis was carried out with an Enraf-NoniusCAD4 diffractometer using MoKα radiation.

EXAMPLES Example 1 Preparation of tetracyano-1,4-hydroquinone frombromanil

Sodium cyanide (23 g; 0.472 mole) was dissolved in 2 L of methanol.2,3,5,6-Tetrabromo-1,4-benzoquinone (bromanil, Lancaster Syntheses,Windham, NH) was added portionwise (25 g; 0.059 mol) over a period ofabout 1 hour. The temperature was allowed to rise to 34° C.; the mixtureturned red. The solution was heated to reflux for 45 minutes, thencooled back to room temperature. HCl gas was bubbled in until the pHreached an indicated 0 to 1 and the mixture turned brown. The mixturewas concentrated under vacuum to dryness, and the residue was extractedseveral times with 1 L of diethyl ether. Morpholine was added to theethereal extract and the red morpholine salt that precipitated wascollected, dried and recrystalized from methanol. There were recovered12.5 g of the crude morpholine salt of tetracyano,1,4-hydroquinone. Themorpholine salt was dissolved in the minimum amount of water, and HClwas bubbled in until the mixture turned yellow and a solid separatedout. This mixture was extracted with ether. The ethereal extracts werecombined, dried over magnesium sulfate, and evaporated to dryness toyield a yellow solid. This solid was then dissolved in 150 ml of water,and the aqueous suspension was filtered to separate insoluble portions.HCl was bubbled into the aqueous filtrate until a yellow, nicelycrystalline solid separated. This mixture was extracted with ether. Theethereal extracts were combined, dried over magnesium sulfate, andevaporated to dryness to yield another yellow solid. This yellow solidwas dissolved in hot acetic acid, and an equal amount of pyrenedissolved in methylene chloride was added. A red complex precipitatedout which was collected, dried and treated with hot dioxane whichresulted in the formation of a dioxane complex. The dioxane complex wasdissolved in water, and the aqueous suspension was filtered to separateinsolubles. HCl was bubbled into the aqueous filtrate until a yellowsolid separated. This mixture was extracted with ether. The etherealextracts were combined, dried over magnesium sulfate, and evaporated todryness to yield another yellow solid. This was recrystallized fromacetic acid to give yellow crystals (1.97 g, 16% yield). Analysis Calc'dfor C₁₀ H₂ N₄ O₂ (Found) % C=57.15 (56.95), % H=0.95(0.95) %N=26.67(26.53), % O=15.24(15.37). Infrared: v(CN) absorptions 2241 and2263 cm⁻¹, v(OH) 3160 br cm⁻¹ ; mp 373° C., with decomposition. Theproduct in solution fluoresces yellow-green.

A repetition of this same procedure on the same scale afforded 2.23 g,18% yield.

Example 2 Preparation of tetracyano-1,4-hydroquinone from bromanil

Reaction between bromanil (6.6 g, 0.0156 mol) and sodium cyanide (4.6 g,0.0935 mol) in 500 ml of methanol was carried out essentially asdescribed in example 1. There was isolated tetracyano-1,4-hydroquinone(0.31 g, 9% yield). Analysis Calc'd for C₁₀ H₂ N₄ O₂ (Found) % C=57.15(56.89), % H=0.95(0.86) % N=26.67(26.17).

Example 3 Preparation of tetracyano-1,4-hydroquinone from2,3-dichloro-5,6-dicyano-1,4-benzoquinone

The reaction of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (10 g, 0.0441mol) with sodium cyanide (9.3 g, 0.190 mol) was carried out in methanol(750 ml) essentially as described in example 1. There were obtained 0.56g, 6% yield of yellow needles.

Example 4 Preparation of the disilver salt oftetracyano-1,4-hydroquinone from tetracyano-1,4-hydroquinone

Tetracyano-1,4-hydroquinone (0.40 g, 0.0019 mol) was dissolved in hotwater (25 ml). Silver nitrate (1.29 g, 0.0076 mol) in water (5 ml) wasadded all at once. The mixture turns black; a precipitate formed. Solidwas collected and dried to give 0.79 g, 99% yield. Analysis Calc'd forC₁₀ N₄ O₂ Ag₂ (Found) % C=28.34 (28.35), % H=0.00(0.14) %N=13.22.(13.27).

Example 5 Preparation of mono tetraethylammonium salt oftetracyano-1,4-hydroquinone

Tetracyano-1,4-hydroquinone (2.30 g, 0.0109 mol) was dissolved in 50 mlof hot water. Tetraethylammonium iodide (7.0 g, 0.027 mol) dissolved in10 ml of hot water was added. The solution was heated to boiling for andthe volume was reduced to about 10 ml. Long orange needles formed uponcooling which were collected and dried under vacuum to yield 2.61 g, 71%yield of tetraethylammonium tetracyano-1,4-benzeneoxide. Analysis Calc'dfor C₁₈ H₂₁ N₅ O₂. (Found) % C=63.70(63.75), % H=6.24(6.10) %N=20.64(20.69). Infrared (Nujol): v(CN) absorptions 2219 cm⁻¹, v,(OH)3515 br cm⁻¹.

Example 6 Preparation of mono tetramethylammonium salt oftetracyano-1,4-hydroquinone (as hydrate)

From tetracyano-1,4-hydroquinone (100 mg, 0.476 mmol) dissolved in 20 mlof hot water and tetramethylammonium bromide (60 mg, 1.05 mmol)dissolved in 10 ml of hot water, 90 mg of tetramethylammoniumtetracyano-1,4-benzeneoxide monohydrate was prepared. Analysis Calc'dfor C₁₄ H₁₃ N₅ O₂. (Found) % C=55.86(56.25), % H=5.021(4.51) %N=23.24(23.17). Infrared: v(CN) absorptions 2218 cm⁻¹ and 2224 sh cm⁻¹.

Example 7 Preparation of the disilver salt oftetracyano-1,4-hydroquinone from tetraethylammoniumtetracyano-1,4-benzeneoxide

Tetraethylammonium tetracyano-1,4-benzeneoxide (0.82 g, 0.00175 mol) wasdissolved in 30 ml of hot water and silver nitrate (1.19 g, 0.007 mol)dissolved in 10 ml of water was added all at once. The mixture turnedblack and a solid precipitated. The solid was collected while themixture was still warm and was dried to give 0.70 g (69% yield) of thedisilver salt. Analysis Calc'd for C₁₀ N₄ O₂ Ag₂ (Found) %C=28.34(28.05), % H=(0.14) % N=13.22(12.90), % O=7.55(8.04). Infrared:v(CN) absorption 2229 cm⁻¹.

Example 8 Preparation of tetracyano-1,4-benzoquinone

Working under a nitrogen atmosphere, bromine (1.06 g, 0.0066 mol)dissolved in 1 ml of dichloromethane was added to a suspension of thedisilver salt of tetracyano-1,4-hydroquinone (0.70 g, 0.00165 mol) in 40ml of dichloromethane. After 1/2 hour agitation at room temperature, theformed silver bromide was filtered off under nitrogen, and the cake waswashed three times with 30 ml of dichloromethane. The filtrate andwashes were combined and evaporated to near dryness and cooled to roomtemperature whereupon small yellow needles separated. These werecollected and dried to give 0.16 g (47% yield) oftetracyano-1,4-benzoquinone. Analysis Calc'd for C₁₀ N₄ O₂. (Found) %C=57.70(57.10), % H=0(0.27) % N=26.92(26.58), % O=15.37(15.95).Infrared: v(CN) absorption 2244 w cm⁻¹, vCO 1698 s cm⁻¹. X-ray crystalstructure analysis confirmed the structure of neutral cyanil. There wasno residual electron density suggesting hydroxyl hydrogens.

Example 9 Preparation of tetracyano-1,4-benzoquinone

In an improvement over the procedure of example 8, working under anitrogen atmosphere, the disilver salt of tetracyano-1,4-hydroquinone(3.10 g, 0.0073 mol) was added all at once to a solution of bromine(4.68 g, 0.0293 mol) dissolved in 50 ml of dichloroethane. After onehour agitation at room temperature, the mixture was heated to reflux for10 minutes to dissolve the organic product, and the silver bromide wasfiltered off hot under nitrogen. The cake was washed four times with 75ml of hot dichloroethane, still under a nitrogen atmosphere. Thefiltrate and washes were combined and evaporated to dryness to give 0.97g (65% yield) of tetracyano-1,4-benzoquinone.

Example 10 Preparation of Ferrocenium 1,4-tetracyanobenzoquinoneide(1:1)

To a solution of ferrocene (22.3 mg, 0.120 mmol) in 5 ml of dryacetonitrile was added a second solution of tetracyano-1,4-benzoquinone(25 mg, 0.120 mmol) in 5 ml of dry acetonitrile. The green mixture waschilled in a refrigerator and the precipitate that formed was collectedand dried to yield 44 mg (94% yield) of black needles. Analysis Calc'dfor C₂₀ H₁₀ N₄ O₂ Fe. (Found) % C= 60.94(60.75), % H=2.56(2.50) %N=14.21(13.88). Infrared (Nujol): v(CN) absorption 2220 cm⁻¹.

Examples 11-19 1:1 Complex formation

Using procedures similar to example 10, 1:1 complexes betweentetracyano-1,4-benzoquinone and the indicated complexing compounds wereprepared.

    ______________________________________                                                             Analysis                                                            Product   Calc'd (Found)                                           Complexing agent                                                                           formula     C      H    N    O                                   ______________________________________                                        11-octamethylfer-                                                                          C.sub.28 H.sub.32 N.sub.4 O.sub.2 Fe                                                      66.41  5.17 11.07                                    rocene                   66.45  5.35 11.04                                    12-decamethylfer-                                                                          C.sub.30 H.sub.30 N.sub.4 O.sub.2 Fe                                                      67.43  5.66 10.49                                                                              5.99                                rocene                   66.96  5.30 10.37                                                                              6.20                                13-tetrathiafulvalene                                                                      C.sub.16 H.sub.4 N.sub.4 O.sub.2 S.sub.4                                                  46.59  0.98 13.58                                                             46.34  0.89 13.31                                    14-N,N,N',N'-tetra-                                                                        C.sub.20 H.sub.16 N.sub.6 O.sub.2                                                         64.51  4.32 22.57                                    methyl-p-phenylene       64.40  4.36 22.19                                    diamine                                                                       15-decamethyl-                                                                             C.sub.30 H.sub.30 N.sub.4 O.sub.2 Co                                                      67.03  5.63 10.40                                    cobaltocene              67.13  5.20 9.52                                     16-hexaazaoctadeca-                                                                        C.sub.28 H.sub.24 N.sub.10 O.sub.2                                                        63.14  4.54 26.31                                    hydrocoronene            63.02  4.72 26.26                                    17-triphenylene                                                                            C.sub.18 H.sub.12 N.sub.4 O.sub.2                                18-hexaaminobenzene                                                                        C.sub.16 H.sub.12 N.sub.10 O.sub.2                                                        51.06  3.22 37.23                                                             51.05  3.09 35.15                                    19-hexamethoxy-                                                                            C.sub.22 H.sub.18 N.sub.4 O.sub.8                                benzene                                                                       ______________________________________                                    

Example 20 2:1 Complex of decamethylcobaltocene withtetracyano-1,4-benzoquinone

The same general procedure as that for the 1:1 complexes was followedexcept for the mole ratio of the reactants. Decamethylcobaltocene (75mg, 0.228 mmol) was allowed to complex with tetracyano-1,4-benzoquinone(24 mg, 0.114 mmol). There was obtained 64 mg (65% yield) of the 2:1complex. Analysis Calc'd for C₅₀ H₆₀ N₄ O₂ Co₂. (Found) %C=69.27(68.96), % H=6.98(6.79), % N=6.46(6.85), % O=3.69(4.04). Infrared(Nujol): v(CN) absorption 2181 s and 2194 m cm⁻¹.

Example 21 Tetracyano-1,4-benzoquinone as hydrogen abstraction reagent

A solution of 9,10-dihydroanthracene (35 mg; 0.192 mmol) dissolved in 1mL dry acetonitrile was reacted with tetracyano-1,4-benzoquinone (40 mg;0.192 mmol) also dissolved in 1 mL dry acetonitrile. After reducing thevolume in half and cooling to -20° C. crystals precipitated and werecollected. The infrared spectra of the precipitate was identical to thatobtained from a mixture of authentic anthracene andtetracyano-1,4-hydroquinone (υ(C.tbd.N)=2239 and 2263 cm⁻¹) verifyingthat tetracyano-1,4-benzoquinone dehydrogenates 9,10-dihydroanthracene.

Example 22 Tetracyano-1,4-benzoquinone as hydrogen abstraction reagent

A solution of 2,3-dichloro-5,6-dicyanohydroquinone (H₂ DDQ) (83 mg; 0.36mmol) dissolved in 5 mL dry acetonitrile was reacted withtetracyano-1,4-benzoquinone (75 mg; 0.36 mmol) also dissolved in 3 mLdry acetonitrile. After reducing the volume and cooling to -20° C.crystals precipitated and were collected. The infrared and VIS-UVspectra of the precipitate were as expected fortetracyano-1,4-hydroquinone (υ(C.tbd.N)=2241 and 2264 cm⁻¹) verifyingthat tetracyano-1,4-benzoquinone dehydrogenates2,3-dichloro-5,6-dicyanohydroquinone and is a stronger hydrogenabstraction reagent than 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ).

What is claimed is:
 1. A process for the preparation of tetracyano-1,4-hydroquinone comprising reacting a tetrasubstituted-1,4-benzoquinone selected from bromanil, chloranil, 2,3,5,6-tetramethoxy-1,4-benzoquinone or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with a source of cyanide ion to generate the desired product in a yield of at least 6%.
 2. The process of claim 1 wherein the source of the cyanide ion comprises an alkali metal cyanide, tetra-aryl ammonium cyanide, or tetra-alkyl ammonium cyanide having an alkyl group of up to 8 carbon atoms.
 3. The process of claim 1 wherein the cyanide ion is in stoichiometric excess during the course of the reaction.
 4. The process of claim 1 wherein the reaction is conducted in a solvent comprising a lower alcohol.
 5. The process of claim 4 wherein the solvent is methanol.
 6. The process of claim 1 further comprising isolation of the tetracyano-1,4-hydroquinone.
 7. The process of claim 6 wherein the final steps of the isolation comprise extraction with water, acidification and extraction with ether. 